MPG & Towing?

C & A s Dad · July 21, 2006

Can anyone tell me if you have experienced any drop in MPG after towing? My Yukon XL has been averaging just over 18MPG and has been doing so for some time. I recently bought a 6500 lb camper and have towed it on 3 short trips. Of course the MPG dropped to 12 to 13 towing the camper but it seems the MPG has not returned to it's normal upper 17s to mid 18s. I do not have a DIC and am relying on only 2 partial tanks that I checked after towing.

My thought is that the PCM has changed it's ratio to help with the towing and it takes it some time to move it back. Is this a crazy idea or could I be right?

The only other change I have made during this time is that I have begun running 93 oct vs 87 oct. I did this at the advise of Snoman and some others on this forum. I have only towed with it once since using 93 but I swear I could feel the difference, especiall when pulling some small hills on my recent trip.

Any comments or info would be appreciated.

asilverblazer · July 21, 2006

Your truck was designed to run on 87 octane, only by advancing the timing will a higher octane really be a noticeable benenfit, and in my case it's minimal. The truck does adjust certain parameters according to driving style, although the few times you tow something ormally isn't enough to offset the majority of the times that you do not tow. I would give it a few tanks, though because small variables can add upt o a decrease (or gain) of 1-2 miles per gallon per tank. (Things like ambient temperature, humidity, tire pressure, prevailing winds, traffic, etc...)

C & A s Dad · July 22, 2006

Thanks

My wife made a 80 mile run yesterday which was mostly interstate driving at just over 70 MPH. I could not help myself so I refilled it this morning and I could pack only 3.95 gallons in it. This is 20 MPG which is the best it has ever gotten.

I realize their are several variables and I cannot use 80 miles as a standard. At least I now know I do not have a problem.

The truck has been averaging just over 18 MPG and I am happy with that considering it is a Yukon XL with 4.10 gears.